Adsorption of cyanide contained in aqueous solution using activated carbon obtained from coffee residue: Absorption efficiency, equilibrium and kinetic model

Abstract

This research aimed to evaluate the adsorption process of CN- contained in synthetic aqueous solution, using activated carbon obtained from coffee residue; studying its efficiency and equilibrium and kinetic models. Fourier transform infrared analysis (FTIR), X-ray diffraction (DRX) and iodine number determination were performed to characterize activated carbon. A composite central design (DCC) with three factors adapted to three levels each and 6 central points was applied to study the effect of pH (A), contact time (B) and adsorbent dosage (C); According to the analysis of variance, all the main factors and the AA interaction were significant in the adsorption efficiency of cyanide on activated carbon, whose maximum value reached was 54.68% and 67.65% for the predictive level. According to the coefficient of determination (R2), Freundlich's isothermal model (0.954) and the three kinetic equations of pseudo second order (0.991, 0.993, 0.993) were adjusted to the experimental process. From the results obtained, the active carbon prepared from coffee residue can be used as a potential adsorbent of CN-, contained in aqueous solutions of low concentrations.